Edge lit sheets have long been known in the art; e.g. U.S. Pat. No. 3,027,669 (Hardesty) and U.S. Pat. No. 3,356,839 (Mehess et al.). Edge lit keypads are also known in the art. For example, U.S. Pat. No. 3,892,959 (Pulles) discloses peripheral cavities for receiving light emitting diodes (LEDs); U.S. Pat. No. 4,177,501 (Karlin) discloses peripheral cavities for receiving light sources; U.S. Pat. No. 4,247,747 (Swatten) discloses LEDs optically coupled to a polyester sheet having a thickness of seven mils (0.18 mm); and U.S. Pat. No. 5,975,711 (Parker et al.) discloses a light conductive panel coupled to a light source.
U.S. Pat. No. 3,998,525 (Giglia) discloses a front lit electrochromic display, wherein the display is on the “back” side of a glass substrate (the side opposite the viewing side). Light is directed into an edge of the substrate. Several sources of light are disclosed.
As used herein, “transparent” does not imply a particular level of light transmission. The amount of light transmission that is suitable depends, among other factors, upon the thickness of the light guide. “Transparent” does imply a sufficient clarity that an image, such as text, is legible or recognizable when viewed through the light guide.
As used herein, “deform” and its cognates are generic to elastic deformation, wherein an article springs back into its original shape when stress is removed, and to plastic deformation, wherein an article is permanently changed in shape.
As portable electronic devices become more common, they are also becoming thinner, which places a premium on reducing the thickness of components. A substrate, light guide, light source, power source, electronics, and display all have finite thicknesses, herein referring to a measurement along the z-axis. The length and width of a device, measured along the x-axis and the y-axis, can have any desired dimension, typically fitting within a pocket on ones clothes. Thickness is typically considerably smaller than the other two dimensions and the desire is for the thickness to be even smaller.
In view of the foregoing, it is therefore an object of the invention to provide a light guide having an integral light source.
It is another object of the invention to provide a light guide having an integral light source, wherein the light guide is also a substrate for conductive traces interconnecting electrical devices.